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... This is an oceanic accumulation zone for floating debris located within the North Pacific subtropical gyre, about halfway between Hawaii and California. Our sightings occurred during an aerial survey in October 2016 that focused on characterising and quantifying ocean plastics through experienced observers and multiple types of sensors (Salgado Kent et al. 2017;Lebreton et al. 2018). ...
... Declination angles from the horizon were recorded for large debris, but not for cetaceans. A more detailed description of our visual survey method is found in Salgado Kent et al. (2017). ...
... We recorded 969 debris items larger than 50 cm in the RGB mosaics ) and logged 311 objects (mostly > 50 cm) in situ during visual surveys (Salgado Kent et al. 2017). These plastics varied in size, colour and type. ...
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Here, we report cetacean sightings made within a major oceanic accumulation zone for plastics, often referred to as the ‘Great Pacific Garbage Patch’ (GPGP). These cetacean records occurred in October 2016 and were made by sensors and trained observers aboard a Hercules C-130 aircraft surveying the GPGP at 400 m height and 140 knots speed. Four sperm whales (including a mother and calf pair), three beaked whales, two baleen whales, and at least five other cetaceans were observed. Many surface drifting plastics were also detected, including fishing nets, ropes, floats and fragmented debris. Some of these objects were close to the sighted mammals, posing entanglement and ingestion risks to animals using the GPGP as a migration corridor or core habitat. Our study demonstrates the potential exposure of several cetacean species to the high levels of plastic pollution in the area. Further research is required to evaluate the potential effects of the GPGP on marine mammal populations inhabiting the North Pacific.
... Plastic waste is now in the public policy spotlight 1 for the ways in which it has altered ocean, as well as terrestrial, 2 ecosystems over the past few decades. 3−5 While efforts to clean up and characterize large quantities of ocean plastic debris are well underway, 6 recent reports provide evidence that the Great Pacific Garbage Patch (GPGP) is rapidly accumulating plastic. 5 The potential adverse effects of microplastic ingestion on human health have also risen as a health concern. ...
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1.Mark-recapture distance sampling (MRDS) methods are widely used for density and abundance estimation when the conventional distance sampling assumption of certain detection at distance zero fails, as they allow detection at distance zero to be estimated and incorporated into the overall probability of detection to better estimate density and abundance. However, incorporating mark-recapture data in distance sampling models raises survey and analysis issues not present in conventional distance sampling. Conversely, incorporating distance sampling assumptions in mark-recapture models raises issues not present in conventional mark-recapture. As a result, being familiar with either conventional distance sampling methods or conventional mark-recapture methods does not on its own put practitioners in good a position to apply MRDS methods appropriately. This paper explains the sometimes subtly different varieties of MRDS survey methods and the associated concepts underlying MRDS models. This is done as far as possible without giving mathematical details – in the hope that this will make the key concepts underlying the methods accessible to a wider audience than if we were to present the concepts via equations.2.We illustrate use of the two main types of MRDS model by using data collected on two different types of survey: a survey of ungulate faecal pellets where two observers searched independently of each other; and a cetacean survey that used a search protocol that could accommodate responsive movement, with only one observer searching independently and the other being aware of all detections.3.Synthesis and applications. Mark-recapture distance sampling is a widely-used method for estimating animal density and abundance when detection of animals at distance zero is not certain. Two observer configurations and three statistical models are described and it is important to choose the most appropriate model for the observer configuration and target species in question. By way of making the methods more accessible to practicing ecologists, we describe the key ideas underlying MRDS methods, the sometimes subtle differences between them, and we illustrate these by applying different kinds of MRDS method to surveys of two different target species using different survey configurations.This article is protected by copyright. All rights reserved.
Chapter
This is a chapter in Advanced Distance Sampling book which is available for purchase.